In the manufacture of power MOSFETs and IGRIs with inversion channels at trench walls, the electric field strength at the edges of the trenches may need to be limited in order not to strain the gate oxide beyond its limits. Some approaches may be to shield the electric field using field plates or using additional p-doped regions in the area of the trench edges. However, these approaches may introduce additional capacities due to the field plates additional capacitances may be formed between the field plate and gate Ciss and/or between the field plate and the drain Crss). In addition, these approaches may lead to the formation of a JHET channel which may lead to an increase of a resistance between the drain and the source, for example.